Since, however, as I have stated, substance is
threefold, viz., genus, species, (and) individual; and (since) we have
set down animality as being the genus, and man the species, as being
already distinct from the majority of animals, but notwithstanding
still to be identified (with animals of his own kind), inasmuch as not
being yet moulded into a species of realized
substance,—(therefore it is, that) when I impart form under a
name to a man derived from the genus, I style him Socrates or Diogenes,
or some one of the many denominations (in use). And since (in
this way, I repeat,) I comprehend under a name the man who constitutes
a species that is generated from the genus, I denominate a substance of
this description individual. For genus has been divided into
species, and species into individual. But (as regards) the
individual, since it has been comprehended under a name, it is not
possible that, according to its own nature, it could be divided into
anything else, as we have divided each of the fore-mentioned (genus and
species).807807
Aristotle’s Categ., c. v.

Aristotle primarily, and especially, and preeminently
entitles this—substance, inasmuch as 102it cannot either be predicated of any Subject,
or exist in a Subject. He, however, predicates of the Subject, just as
with the genus, what I said constituted animality, (and which is)
predicated by means of a common name of all particular animals, such as
ox, horse, and the rest that are placed under (this genus). For
it is true to say that man is an animal, and horse an animal, and that
ox is an animal, and each of the rest. Now the meaning of the
expression “predicated of a Subject” is this, that inasmuch
as it is one, it can be predicated in like manner of many
(particulars), even though these happen to be diversified in
species. For neither does horse nor ox differ from man so far
forth as he is an animal, for the definition of animal is said to suit
all animals alike. For what is an animal? If we define it,
a general definition will comprehend all animals. For animal is
an animated Substance, endued with Sensation. Such are ox, man,
horse, and each of the rest (of the animal kingdom). But the
meaning of the expression “in a Subject” is this, that what
is inherent in anything, not as a part, it is impossible should exist
separately from that in which it is. But this constitutes each of
the accidents (resident) in Substance, and is what is termed
Quality. Now, according to this, we say that certain persons are
of such a quality; for instance, white, grey, black, just, unjust,
temperate, and other (characteristics) similar to these. But it
is impossible for any one of these to subsist itself by itself; but it
must inhere in something else. If, however, neither animal which
I predicate of all individual animals, nor accidents which are
discoverable in all things of which they are nonessential qualities,
can subsist themselves by themselves, and (yet if) individuals are
formed out of these, (it follows, therefore, that) the triply divided
Substance, which is not made up out of other things, consists of
nonentities. If, then, what is primarily, and pre-eminently, and
particularly denominated Substance consists of these, it derives
existence from nonentities, according to Aristotle.